Method of producing metallurgical coke

ABSTRACT

A method of manufacturing metallurgical coke, consisting in that poor-caking coal is ground, then molded at a temperature of 20*350* C., whereupon the coal briquettes are caked at 450*-600* C. under the pressure of vapor and gaseous products of the coal thermal decomposition, and are then calcined at 750*-950* C.

United States Patent Dzhaparidze et al.

[ 51 May 16, 1972 METHOD OF PRODUCING METALLURGICAL COKE Inventors:Platon Nesterovich Dlhaparldu, ulitsa Uplistsikhskaya, 2; LeonidAlexeevich Drakin, ulitsa Kominterna, 39, korpus 26, kv. 45, both ofTbilisi; Sergei Ivanovich Malyshev, Panfilovsky perevlok, 3, kv. 37,Moscow, all of U.S.S.R.

Filed: Jan. 27, 1970 Appl. No.: 6,251

U.S. Cl ..44/l0 H, 44/10 K, 201/6 Int. Cl. ..Cl0l 5/00 Field of Search..44/l0 R, l0 H, l R, 10 K;

References Cited UNITED STATES PATENTS Primary Examiner-C. F. DeesAttorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT 5 Claims, 1Drawing Figure METHOD OF PRODUCING METALLURGICAL COKE The inventionrelates to methods of producing metallurgical coke from a poor-cakingcoal.

Metallurgical coke is one of the main constituents of the blast furnaceburden, and it finds wide application in the smelting of cast-iron,steel, and ferro-alloys.

Known in the art is a method of obtaining metallurgical coke frompoor-caking coal, consisting in that coal is ground and then subjectedto rapid heating with a gaseous heat carrier up to a temperature,whereat it converts into plastic state, and is molded on a cellulated orplate conveyer at a temperature of 400-420 C., the formed briquettesbeing fed into a continuous action oven where they are caked at atemperature of 450-600 C. and calcined at 750-95 C. (see USSR Author'sCertificate No. 149091, cl. a, 22/07).

The disadvantages of the previous method are a cumbersome processsequence, and difficulties in stabilizing the process of heating andmolding the coal during its conversion into plastic state, which causediscontinuities of the process and production of considerable amounts oflow quality coke.

Besides, caking and calcining in one apparatus (oven) involves acomplicated design of this apparatus, since said processes are carriedout at different rates.

The object of the present invention is to work out new conditions ofmolding and caking in the method of producing metallurgical cokeconsisting in grinding poor-caking coal, molding it, caking thebriquettes at a temperature of 450-600 C., and their calcining at750-950 C.

In accordance with said and other objects, the invention consists inthat molding is done at a temperature of -350 C. (before coal conversioninto plastic state), and caking is carried out under the pressure ofvapor and gaseous products of coal thermal decomposition.

Molding coal before its conversion into plastic state significantlysimplifies and stabilizes this operation, owing to the fact that beforeconverting into plastic state coal has constant physical and chemicalproperties, does not swell, and does not release any products of itsthermal decomposition.

At the same time the use of the vapor and gas pressure while caking thecoal briquettes without any air access largely improves their bakingconditions, widens the temperature limits and the time range of coalplasticity, raises the steadiness and stability of the coal cakingprocess as a whole.

The pressure of the vapor and gaseous products during the process ofcaking the briquettes is advisable to be kept within l-20 atm. gauge.

In case molding is done on a cellulated conveyer, it is advisable to becarried out too under the pressure of vapor and gaseous products of coalthermal decomposition, the value of this pressure being equal to that incaking.

For the purpose of utilizing the heat of the exhaust vapor and gaseousproducts of coal thermal decomposition, as well as the bindingproperties thereof, the fined coal is pitched with said products priorto moulding.

The proposed method of producing metallurgical coke is realized asfollows.

The poor-caking coal is ground to a size of 0-3 mm moistened, whenevernecessary, to l5-l8 percent of moisture content or pitched with theproducts of its thermal decomposition, molded at a temperature of 20350C. and at atmospheric pressure to a density of 0.9-1.1 g./cm and thenthrough a sluicing arrangement charged, together with the die molds,into a travelling oven to cake the briquettes. The caking is carried outunder the pressure of the vapor and gaseous products of coal thermaldecomposition. In the course of movement of the plate conveyer the coalbriquettes are heated to a temperature of 450-600 C. at a rate of 2-6per minute, which results in their caking. The oven is heated byelectric heaters or a gaseous heat carrier, with a gradual increase ofthe oven temperature in the direction of the discharge of the bakedbriquettes.

In the process of baking, moisture is evaporated and products of coalthermal decomposition are released, thus building up a pressure in theoven and promoting the caking of the coal briquettes. The required valueof the vapor and gas pressure is chosen on the basis of the coal natureand its physical and chemical properties.

To obtain well caked briquettes, the value of the vapor and gas pressureis recommended to be maintained within 1 20 atm. gauge, proceeding fromthe coal properties and the requirements demanded of the briquettes. Theexcess pressure of the vapor and gaseous products built up in the courseof caking, is continuously relieved. At the turning point of the plateconveyer i.e. opposite the sprocket, the caked briquettes are removedtogether with the die mold, and are through a sluicing arrangementdischarged from the oven. After discharging the die molds, the cakedbriquettes are subjected to further heat treatment (calcining) inordinary continuous shaft furnaces. In the shaft furnaces the briquettesare heated to a temperature of 750-950 C.

Separation of the operations of caking and calcining, and theirperformance in separate apparatuses permits significantly simplifyingthe design of the caking apparatus,and raising its productiveefficiency.

In case of carrying out the coal molding process on a cellulatedconveyer under the pressure of vapor and gaseous products of coalthermal decomposition, the proposed method of producing metallurgicalcoke is carried out as is described below and explicated in the processdiagram.

According to the diagram, coal ground to a size of 0-3 mm is through asluicing arrangement 1 fed by worm 2 into a travelling oven 3 onto acellulated conveyer 4. On this cellulated conveyer the coal is at atemperature of 20-350 C. compacted by a molding arrangement 5 to adensity of 0.9 1.1 gJcm.

When molding coal within temperatures of 20-l00 C. the coal moisturecontent is advisable to be kept at 15-18 percent, water or water steambeing fed at point A of worm 2. When molding coal within temperatures ofl00-350 C., the coal is pitched with the products of its thermaldecomposition, the excess pressure of the vapor and gaseous productsbeing released through valve 6.

Coal briquettes continuously moved along the furnace on a cellulatedconveyer are heated (baked) to a temperature of 450-600 C. at a rate of2-6 per minute. Oven 3 is heated by electric heaters 7 or by gas with agradual temperature rise in the direction of the discharge of the cakedbriquettes. As it was said earlier, in the process of caking moisture isevaporated, and products of coal thermal decomposition are released,which build up pressure in the oven and help coal caking. To obtain wellcaked briquettes, the pressure in the oven is advisable to be maintainedwithin l-20 atm. gauge. The excess pressure of the vapor and gaseousproducts is continuously released through valves 6 and 8.

During the turn of the celluated conveyer on the sprocket the cakedbriquettes freely fall out from the opening cells and are through asluicing arrangement 9 discharged from the oven. The further heattreatment (calcining) of the caked briquettes is carried out in ordinarycontinuously acting shaft furnaces at a temperature of 750-950 C.

The described process sequence can be realized so, that mounted in onetravelling oven will be two conveyers: a cellulated conveyer whereon thecoal is molded, and a plate conveyer whereon the briquettes are baked,the conditions of coal molding and briquettes caking remainingunchanged.

For better understanding of the present invention given herein are thefollowing examples of how to realize the proposed method of producingmetallurgical coke.

EXAMPLE 1 Having 632 g. of coal (moisture content 5.7 weight percent,ash content 12.86 weight percent, volatile matters content 39.42 weightpercent, the plastic layer thickness 8 mm) ground to a size of 0-3 mm,added thereto were 88 g. of water, the batch being then thoroughlymixed, charged into two four-cell metal molds, and pressed in ahydraulic press at a pressure of 100 kg/cm to a density equaling l g./cm(i.e. to the volume of the whole batch equaling 720 ml).

The die molds with the pressed in coal were placed into an autoclave of8 liter capacity, and were heated to a temperature of 550 C. at a rateof 4 per minute. When the temperature was 250 C. the pressure of thevapor and gaseous products in the autoclave rose to 10 atm. gauge. Thispressure was kept up until the end of the experiment by relieving theexcess pressure of the vapor and gaseous products of coal thermaldecomposition. After 2 hours and 17 minutes the temperature in theautoclave reached 550 C. At this temperature caking was completed, andthe pressure was released from the autoclave. After the autoclave cooledoff, the die molds were taken out and the caked briquettes dischargedfrom the molds.

Visual examination of the briquettes showed that they were well baked,porous, gray-colored, the surface of the briquettes being smooth,without any visible cracks. Two briquettes of the eight produced weretested by throwing them from a height of 2 meters onto a wooden floor.The tests have proved that one briquette stood three throwings, andanother one could stand five.

The remaining six briquettes were placed into porcelain cups with acapacity of 450 ml each (two briquettes in a cup), a layer of asbestoscovering them on top and fine coke being spilt thereover to prevent thebriquettes from burning out. Then the cups were charged into a mufi'lefurnace to heat (calcine) the briquettes to a temperature of 800 C. at arate of 2 per minute.

EXAMPLE 2 Poor-caking coal with characteristics given in Example 1 wascaked. The caking was carried out so, as is described in Example 1, withthe only difference that the coal briquettes were baked in the autoclaveunder a pressure of the vapor and gaseous products equaling atm. gauge.

EXAMPLE 3 Caking was carried out of poor-caking coal withcharacteristics indicated in Example 1. The caking process was carriedout so, as is described in Example 1, with the only exception that thecoal briquettes were baked under a pressure of the vapor and gaseousproducts equaling 2 atm. gauge.

EXAMPLE 4 Poor-caking coal was baked similarly to Example 1, with theonly difference that instead of moistening the coal prior to itsmolding, it was pitched by the vapor and gaseous products of its thermaldecomposition. To realize the pitching process, the coal batch (632 g.)was placed into a Buchner funnel, which was then closed with a layer ofasbestos. After that the funnel with coal was placed into an electricstove or a thermostat to be heated to a temperature of 150 C. Passedthrough the heated coal were the vapor and gaseous products divertedfrom the autoclave during the release of the excess pressure at thestage of the briquettes caking in Example 1. The pitched coal was mixed,and then subjected to molding and further treatment, as in Example 1.

The quality characteristics of the metallurgical coke obtained aftercalcining the baked briquettes in Examples l-4, is presented in thefollowing table.

The strength given in the table was determined by a method consisting inthat a batch of coke weighing 20 g. with a medium lump size of 9-l 3 mmwas tested by throwing thereon 15 times a load of 1 kg from a height of1 m. The strength was determined as the ratio of the work done TABLEPressure Technical analysis, weight of vapour percent and gaseousproducts Exin the au- Ash Volatile I ample toclave, Moisture conmattersPorosity, Strength, number atm. g.p. content tent content percent kgJdm.

( 15 kg) to S, i.e. the surface formed as a result of the work.

As is clear from the above table, the quality characteristics of thecoke produced by the proposed method complies with the principalrequirements demanded of metallurgical coke (porosity 50.80 54.86percent, strength 6.00 7.53 kgldm Although the present invention isdescribed with reference to the preferred embodiment thereof, it standsto reason that variations and alterations are possible without divertingfrom the idea and scope of the invention, which will be readilyunderstood by those skilled in the art. These variations and alterationsare to be considered as within the confines of the idea and scope of theinvention and the appended claims.

What we claim is l. A method of producing metallurgical coke, comprisinggrinding poor-caking coal, molding the thus ground coal at a temperatureof 20 to 350 C. to form briquettes, caking the coal briquettes at atemperature of up to 450 to 600 C. within about 2 hours under thepressure of the vapor and gaseous products of the coal thermaldecomposition, and then calcining the briquettes at a temperature of upto 750- 950 C.

2. A method as claimed in claim 1, wherein the pressure of the vapor andgaseous products is equal to l 20 atm. gauge.

3. A method as claimed in claim 1, comprising effecting the molding on acellulated conveyor transporter under the pressure of the vapor andgaseous products of coal thermal decomposition, the latter being equalto the pressure of said products during caking the briquettes, theduration of molding being determined by that of the caking of thebriquettes.

4. A method as claimed in claim 3, wherein prior to molding, the groundcoal is pitched with the vapor and gaseous products of its thermaldecomposition.

5. A method as claimed in claim 1, wherein prior to molding, the groundcoal is pitched with the vapor and gaseous products of its thermaldecomposition.

2. A method as claimed in claim 1, wherein the pressure of the vapor andgaseous products is equal to 1 - 20 atm. gauge.
 3. A method as claimedin claim 1, comprising effecting the molding on a cellulated conveyortransporter under the pressure of the vapor and gaseous products of coalthermal decomposition, the latter being equal to the pressure of saidproducts during caking the briquettes, the duration of molding beingdetermined by that of the caking of the briquettes.
 4. A method asclaimed in claim 3, wherein prior to molding, the ground coal is pitchedwith the vapor and gaseous products of its thermal decomposition.
 5. Amethod as claimed in claim 1, wherein prior to molding, the ground coalis pitched with the vapor and gaseous products of its thermaldecomposition.